Machine Learning and the Hunt for ET

Often we see machine learning being used to deal with data sets of such a vast scale that it boggles the mind, but how is machine learning being used to tackle one of the most important questions, are we alone?

The Milky Way Galaxy consists of an estimated 100 billion star systems, with our own solar system sitting on the edge of one of the Orion arm, about 2/3rds of the way from galactic centre. Our telescopes have barely scratched the surface as to what we have so far observed. One such mission is the endeavors of the Kepler orbital observatory which monitors the brightness of 150,000 stars in our local region.

The aim of Kepler is to find planets orbiting distant stars, by looking for the tiniest variations in a star’s luminosity. While our telescopes are nowhere near powerful enough to directly observe the planets themselves, we can observe the brief shadows and gravitational distortions they make as they orbit around their star.

The researchers working with the data Kepler looks for these tiny variations to identify planets, but manually checking the data for hundreds of thousands of systems is laborious and objects can be overlooked. NASA has turned to using machine learning to aid in the search, by entering the same criteria that the scientists have been using to check data. The results were then tested against pre-checked systems and the solution had a 96% success rate.

In fact the machine learning algorithms were detecting worlds that scientists had missed, for instance discovering an 8th planet orbiting the main-sequence star Kepler-90. This tied the Kepler-90 system with our own Solar System for the record of the most planetary bodies orbiting a single star.

From this data, scientists can also work out the size of the planet, its distance from its parent star and its composition. These alien worlds are each unique and bizarre, highlighting the limitless possibilities of the universe and how much we still have to learn. Such previously discovered planets include:

The planet 55 Cancri orbits extremely close to its star, and is a world where a year lasts only 18 hours. The planet is tidally locked meaning that one side is always facing its star, there is no day and night cycle. The planet is believed to have a rocky core, surrounded by water that is heated to such temperatures that it exists in a ‘supercritical’ state, where it is neither a gas nor a liquid. A layer of steam exudes from the planet as the water hits the cooler upper atmosphere, it is a world of extremes that no human could ever survive on.

Kepler 22-b orbits just far enough from its star that water can exist as a liquid on its surface, with a fairly moderate surface temperature (known as the Goldilocks Zone). Scientists speculate that the world has a small rocky core surrounded by a vast planet encompassing ocean. On such a world huge storms and tsunamis, pulled by the gravitational fields of surrounding bodies, generate waves the size of the tallest mountains on Earth.

Finally we reach Kepler-186f, a planet which is a similar size to our own Earth and orbiting within its star’s Goldilocks Zone. It is speculated to be a rocky world where liquid water can exist on its surface. Although it receives 1/3rd of the light that Earth receives, meaning that the brightest it gets would be equivalent to our own sunsets. It represents one of the most likely candidates for life yet found. Perhaps under the twilight clouds of this world, alien minds are looking upon our own pale blue dot and wondering what we might be like.

As machine learning tools become more and more powerful, and as more strange worlds are discovered, our perceptions about the universe will change. Maybe one day, we might finally find out whether the truth is out there.